U.S. Pat. No. 4,903,410 discloses a guide bar of the kind referred to above wherein longitudinal cutouts are provided in the side parts for saving weight. These cutouts are filled out with a bonded fiber insert with the insert itself defining the center part disposed between the two side parts. The outer parts are made of steel and are connected to each other at several locations by electrowelding. Form parts which can be electrowelded are arranged between the two side parts with the thickness of the form parts corresponding approximately to the thickness of the spacer plate made of non-conducting material. The form parts are arranged at approximately equal spacings in a row one behind the other and extend through round cutouts which are provided in the peripheral region of the spacer plate defining the center part. These form parts have the task of establishing the electrical connection between the side plates made of steel in order that a trouble-free electric welding of the two side plates is obtained. The center spacer plate is made of a glass fiber bonded material and is disposed between the side plates. The spacer plate is held with the aid of electrically conducting bolts which extend through the spacer plate. This configuration leads to a comparatively large weight reduction while providing satisfactory stability of the bar. However, this configuration has the disadvantage that its manufacture is relatively expensive. The production is especially expensive because of the required form parts (such as steel bolts) that extend through corresponding openings of the center part and which are to be seated between the side parts.
U.S. Pat. No. 3,545,505 discloses another guide bar which likewise comprises two side parts lying in spaced relationship to each other which have round openings disposed close to each other along the greatest part of their respective lengths for the purpose of saving weight. The center part of this known bar is made of plastic which also fills out the round cutouts in the two side parts with the round cutouts having undercuts in the side parts by means of which the injected plastic layer is held tightly between the side plates. In this embodiment, it is disadvantageous that the injected plastic center part also defines the connection to the side plates and this connection does not permanently withstand the high stresses which act on the guide bar when working with the chain saw. These stresses are produced by bending and/or transverse forces.